In ink-jet printing methods, droplets of ink are directly projected onto a printing medium from very fine nozzles and allowed to adhere to the printing medium to form characters or images thereon. The ink-jet printing methods have now been extensively employed not only in printing applications for ordinary consumers but also recently in commercial and industrial printing applications because of various advantages such as easiness of full coloration, low cost, capability of using a plain paper as the printing medium, non-contact with printed characters or images, etc.
In the commercial and industrial printing applications, there has been proposed the high-speed printing method in which a rolled synthetic resin film is scanned using a stationary printing head of a line printing type.
Since the synthetic resin films are incapable of absorbing an ink therein, the ink printed on the films tends to still exhibit high flowability even after droplets of the ink are impacted onto the films, and tends to suffer from occurrence of intercolor bleeding and deterioration in quality of characters or images printed thereon. For this reason, in order to efficiently dry the ink printed on the films, ink-jet printing methods using various drying means have been proposed.
For example, JP 2008-44367A (Patent Literature 1) discloses an image-forming apparatus including a heating means capable of selectively heating an optional part of a printing medium and a control means for controlling the heating means, in which the printing medium is heated prior to ejection of a liquid thereonto according to such a heating pattern that a heating temperature in a region of the printing medium where a rate of ejection of the liquid is not less than a predetermined value is adjusted to a first set temperature that is not higher than an allowable heating temperature of the printing medium, and a heating temperature in another region of the printing medium where a rate of ejection of the liquid is not more than the predetermined value is adjusted to a second set temperature that is lower than the first set temperature.
JP 2013-166271A (Patent Literature 2) discloses an ink-jet printing method using a printing apparatus that includes a printing head provided with ink ejection nozzles and a heating means capable of heating a printing medium from a rear side surface of the printing medium opposed to a front side surface thereof on which the nozzles are disposed, said method including the step of drying an ink containing a solvent, a colorant and a resin using the heating means after the ink is impacted on the printing medium. In Patent Literature 2, as is apparent from the figures shown therein, there is used the printing apparatus that includes the heating means capable of heating the printing medium from a rear side surface thereof, in which the heating means is disposed just below the ink-jet printing head.